A numerical based study was conducted to further understanding of turbine tip leakage and flow mechanisms for squealer tip blade. Three blade geometry models with different tips are established. They are squealer tip blade, squealer tip with injection holes blade, squealer tip with injection and film cooling holes blade, separately. Coupled aerodynamic and heat transfer numerical simulation method is used to study blade tip flow and heat transfer based the whole blade computational model. The results show that tip coolant injection will perform a positive effect for the resisting tip leakage, and it will reduce the temperature of blade tip surface and squealer rim, greatly. Film cooling near tip can cool blade squealer rim effectively, but it brings extra total pressure loss.